Toxicity testing is a necessary and time-consuming part of the pharmaceutical drug development pipeline. A more rapid screen to detect toxicity of lead drug candidates may be the use of gene expression microarrays. For example, microarrays consisting of full length genes or gene fragments on a substrate may be formed. These arrays can then be tested with samples treated with the drug candidates to elucidate the gene expression pattern associated with treatment with the drug candidate. This gene pattern can be compared with gene expression patterns of compounds associated with known toxicological responses.
Benzo(a)pyrene is a known rodent and likely human carcinogen and is the prototype of a class of compounds, the polycyclic aromatic hydrocarbons. It is metabolized by several forms of cytochrome P450 and associated enzymes to both activated and detoxified metabolites Degawa et al. (1994) Cancer Res. 54: 4915-4919). The ultimate metabolites are the bay-region diol epoxide, benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE) and the K-region diol epoxide, 9-hydroxy benzo(a)pyrene-4,5-oxide, which have been shown to cause DNA adduct formation (alkylation of guanine bases). DNA adducts have been shown to persist in rat liver up to 56 days following treatment with benzo(a)pyrene at a dose of 10 mg/kg body weight 3 times per week for 2 weeks (Qu and Stacey, (1996) Carcinogenesis 17: 53-59).
Acetaminophen is a widely-used analgesic. It is metabolized by specific cytochrome P450 isozymes with the majority of the drug undergoing detoxification by glucuronic acid, sulfate and glutathione conjugation pathways (Chen et al. (1998) Chem. Res. Toxical 11: 295-301). However, at high nontherapeutic doses, acetaminophen can cause hepatic and renal failure by being metabolized to an active intermediate, N-acetyl-p-benzoquinone imine (NAPQI). NAPQI then binds to sulfhydryl groups of proteins causing their inactivation and leading to subsequent cell death (Kroger et al. Gen. Pharmacol. (1997 28: 257-263).
Clofibrate is an antilipidemic drug which lowers elevated levels of serum triglycerides. In rodents, chronic treatment produces hepatomegaly, an increase in hepatic peroxisomes Lock et al. (1989) Ann. Rev. Pharmacol. Toxicol. 29: 145-163). Clofibrate has been shown to increase levels of cytochrome P450 4A and reduce the levels of P450 4F (Kawashima et al. (1997) Arch. Biochem. Biophys. 347: 148-154).
It is also involved in transcription of .beta.-oxidation genes as well as induction of peroxisome proliferator activated receptors Kawashima supra.
The present invention provides compositions and methods for the screening, preferably in a microarray format, of compounds and therapeutic treatments for toxicological effects.